=2D----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

It's a good weekend for home improvement, so I thought I'd tune my
antennas and replace my coax with longer runs to suit where I'd like
to place my station. I figured now was a good time to build in an RF
choke in an attempt to remove interference and hopefully be able to
receive HF, but there are no online resources with formulas or
anything. I was hoping for something like the innumerable dipole
calculators out there -- something where I could input a frequency and
a diameter, then select a type of coax, and hit a button to find out
how many turns.

Most online references are very vague, so I'm just going to
experiment. I was hoping, though, that someone could direct me to a
useful reference. I have an PDF of an old QST article which says that
W7EL has a table in the Antenna Handbook. A friend of mine has a copy
of the Antenna Handbook, but she may have lost it in the move.

Any suggestions? Right now, I'm going to experiment with different
values and see what I can discover, but it can't hurt to hear about
what others have done.

Jack.
=2D --=20
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
=2D----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (FreeBSD)

iD8DBQE/de+TGPFSfAB/ezgRAk2IAJ9Aanda0CutUlFZlIvY+3ZTmD+fsACgsXdu
Cg8I9KSeVlmvo+QNs7pmaKg=3D
=3DmHAv
=2D----END PGP SIGNATURE-----

On Sat, 27 Sep 2003 13:14:06 -0700, Jack Twilley
wrote:


Most online references are very vague, so I'm just going to
experiment. I was hoping, though, that someone could direct me to a
useful reference. I have an PDF of an old QST article which says that
W7EL has a table in the Antenna Handbook. A friend of mine has a copy
of the Antenna Handbook, but she may have lost it in the move.

Any suggestions? Right now, I'm going to experiment with different
values and see what I can discover, but it can't hurt to hear about
what others have done.

Jack.

Hi Jack,

Do an advanced search in Google for this newsgroup using the keywords
Choke, and W7EL which would bring up a several dozen hits easily and
at least a couple could fill in the gaps with that table.

73's
Richard Clark, KB7QHC

To design self-resonant, single-layer chokes, starting with any length and
any diameter and number of turns of wire or coax, download program SOLNOID3.
This program will also estimate the temperature rise above ambient when a
given RF voltage is applied across it. And a lot of other features.

To make a current/choke balun, such as may be fitted between a balanced line
and a tuner, just wind 8 or 10 turns spaced turns of 18 or 20 gauge twin
speaker cable around a 1.75" or 2" diameter ferrite ring. Use HF grade
ferrite.

But best way to choke a coax feedline is to slide 10 or more ferrite hollow
cylinders over it. Space them out if you like.

For easy design of 4-to-1 impedance ratio voltage-baluns, using speaker-type
twin cable, download program TOROID.
----
=======================
Regards from Reg, G4FGQ
For Free Radio Design Software
go to http://www.g4fgq.com
=======================

On Sat, 27 Sep 2003 20:29:50 GMT, Richard Clark
wrote:

On Sat, 27 Sep 2003 13:14:06 -0700, Jack Twilley
wrote:


Most online references are very vague, so I'm just going to
experiment. I was hoping, though, that someone could direct me to a
useful reference. I have an PDF of an old QST article which says that
W7EL has a table in the Antenna Handbook. A friend of mine has a copy
of the Antenna Handbook, but she may have lost it in the move.

Any suggestions? Right now, I'm going to experiment with different
values and see what I can discover, but it can't hurt to hear about
what others have done.

Jack.

Hi Jack,

Do an advanced search in Google for this newsgroup using the keywords
Choke, and W7EL which would bring up a several dozen hits easily and
at least a couple could fill in the gaps with that table.

The ARRL Handbook as well as the ARRL Antenna book also have
information on them.

The ones I've seen use roughly an 8 inch diameter coil with the turns
varying to suit the lowest frequency covered.

I know one of them has a rule of thumb for the number of turns and I
don't remember how many turns I've used in the past, but "I think" I
may have used about 6 or 8 turns for 20 meters. "As I recall" (please
note all the weasel words so don't take the numbers for specifics) It
takes about 40 feet of cable wound up in the 8 inch diameter coil for
160 meters.

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)

73's
Richard Clark, KB7QHC

I assume the article is referring to the coil dimensions in the _ARRL
Handbook_. Each coil works best over about three bands. I highly
recommend both the _ARRL Handbook_ and the _ARRL Antenna Book_. Not all
the world's knowledge is on line yet.

If you have an antenna analyzer, you can measure the impedances of your
experimental chokes. Twist the center conductor and shield together at
both ends of the coax. Connect one end to the center conductor of the
analyzer, and the other to the analyzer body. Adjust the coil for the
highest impedance at the frequency or frequencies of interest.

Roy Lewallen, W7EL

Jack Twilley wrote:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

It's a good weekend for home improvement, so I thought I'd tune my
antennas and replace my coax with longer runs to suit where I'd like
to place my station. I figured now was a good time to build in an RF
choke in an attempt to remove interference and hopefully be able to
receive HF, but there are no online resources with formulas or
anything. I was hoping for something like the innumerable dipole
calculators out there -- something where I could input a frequency and
a diameter, then select a type of coax, and hit a button to find out
how many turns.

Most online references are very vague, so I'm just going to
experiment. I was hoping, though, that someone could direct me to a
useful reference. I have an PDF of an old QST article which says that
W7EL has a table in the Antenna Handbook. A friend of mine has a copy
of the Antenna Handbook, but she may have lost it in the move.

Any suggestions? Right now, I'm going to experiment with different
values and see what I can discover, but it can't hurt to hear about
what others have done.

Jack.
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (FreeBSD)

iD8DBQE/de+TGPFSfAB/ezgRAk2IAJ9Aanda0CutUlFZlIvY+3ZTmD+fsACgsXdu
Cg8I9KSeVlmvo+QNs7pmaKg=
=mHAv
-----END PGP SIGNATURE-----